But he has to take drugs to suppress his Persona, like the members of Strega, since he isn't naturally compatible with the power. The drugs lose their effectiveness over time, so eventually, it will overwhelm and kill him.
How so? If you mean that sex automatically makes one an adult then you are sadly mistaken. Maturity makes a person an adult. There are many people who fuck and act like total children.
The way I thought of it was that he is able to use his persona naturally, but because his persona is unstable, he took the pills to keep it under control. The members of Strega took the pills to get their powers. I think?
You're both sorta right; his persona went out of control and accidentally ended up killing Ken's mom, so he took pills to control it so nothing like that would ever happen again. I think it's possible he would've learned to control it over time even without the pills, but I don't think he'd want to risk killing his best friends either. As for Strega, I do believe it's a similar deal where they just can't control them. But man, FeMC doesn't need to have a freudian excuse to be a raging shotacon.